Effects of a biomimetic dual-analogue primer on the bonding performance of an experimental ion-releasing adhesive system - An in vitro study.

OBJECTIVES: This study evaluated at baseline (T0) and after thermocycling (TC) the dentine bonding performance of an experimental bonding system containing fluoride-doped calcium phosphate (FDCP) used in combination with a biomimetic dual-analogue dentine conditioner (PRM). Their effect on dentine enzymatic activity was also evaluated, along with fractographic and ultramorphology/nanoleakage characteristics. METHODS: An experimental FDCP-containing primer and bond resin system was generated and applied on dentine with or without PRM. Controls included a commercial universal adhesive (SCH) and a glass ionomer cement (GIC). Resin-dentine matchsticks were created and subjected to microtensile bond strength (microTBS) testing at 24 h or after thermo-aging (10,000 cycles). Failure mode and fractographic SEM analyses were performed post-microTBS test. Interfacial characteristics and in situ zymography were evaluated through confocal microscopy at T0 and after TC. Gelatine zymography was performed on protein extracts from dentine powder pretreated with the tested materials. Data from the microTBS test were statistically analysed (alpha = 0.05). RESULTS: SCH showed a significant drop in microTBS (p < 0.05) with adhesive failures and collagen degradation often observed after TC. GIC specimens had the lowest microTBS values (p < 0.05), but no significant drop after TC (p > 0.05). The experimental system was characterised by lower microTBS values than SCH, but with no significant drop after TC (p > 0.05). However, specimens in the experimental groups showed at the bonding interface evident mineral deposition, with less enzymatic activity compared to controls. CONCLUSIONS: The FDCP-containing experimental adhesive system maintained the bonding performance after TC, protecting the hybrid layer especially when used in combination with PRM. CLINICAL SIGNIFICANCE: Innovative ion-releasing restorative systems play a crucial role in preserving the integrity of hybrid layers. These systems promote a remineralisation process that not only reinforces the hybrid layers but also inhibits dentine proteolytic enzymes, thereby enhancing the chances of creating long-lasting dental restorations.